Field of the Invention
The present invention relates an optical apparatus and an image pickup apparatus, and more particularly to an optical apparatus capable of obtaining polarization information and an image pickup apparatus having the same.
Description of the Related Art
There is known an image pickup apparatus configured to emphasize and detect a predetermined characteristic of an object by observing a polarization state of light from the object. For example, when images are captured by changing a transmitting polarization direction with a single-lens reflex camera in which a polarization filter is attached to its lens front surface, a highlighting effect of a texture, such as a color and contrast of an object, and a highlighting or reducing effect of an image of reflected light of a water surface etc. can be obtained. Furthermore, there is known an inspection apparatus which detects an edge or a defect portion of an object by capturing images with different polarization directions.
Japanese Patent No. 5,682,437 discloses a configuration of an image pickup element that includes a wire grid polarizer that transmits different polarized light for each pixel on a solid-state image pickup element and extracts polarization information from a plurality of pixels. U.S. Patent Application Publication No. 2009/0079982 discloses a configuration that includes a quarter waveplate, two retardation plates having a variable retardation, and a polarizer, and obtains part of a Stokes parameter by changing an axial direction of each retardation plate and by generating a plurality of images.
However, Japanese Patent No. 5,682,437 requires a plurality of pixels to obtain the polarization information, and the resolution and the color information are lost. U.S. Patent Application Publication No. 2009/0079982 expensively needs two variable retardation plates and a complicated control. Further, if a common digital single-lens reflex camera has an optical low pass filter and an autofocus unit arranged before an image pickup apparatus having polarization dependency, using the configuration disclosed in Japanese Patent No. 5,682,437 or U.S. Patent Application Publication No. 2009/0079982 may not obtain the polarization information of the object appropriately.